Enhancing performance of NiCo2S4/Ni3S2 supercapacitor electrode by Mn doping

Several transition metal sulfides have been studied as electrode materials for supercapacitor. With high electrical conductivity and theoretical capacity, NiCo2S4 have gained much attention in this field where several methods are employed to enhance its performance. In this work, the effects of Mn doping on electrochemical performances of NiCo2S4/Ni3S2 electrodes are investigated. The electrodes were prepared by a facile hydrothermal method with an addition of MnCl2, which not only gives Mn ion but also influences pH of the solution and the electrodes' morphology. With small amount of Mn, capacity of the doped electrode is enhanced by a maximum of 160% resulting in a capacity of 145 mAh/g (or 1350 Fg(-1) in capacitance). At the same time, the nanosheet feature, good cycle stability, and rate capability of the electrode are preserved. Experiments and computations suggest that the increased capacity is caused by the increased electrical conductivity and the improved interaction between Co metal center on the electrode surface and OH- ion in the electrolyte. Thus, it is shown that doping metallic ions into NiCo2S4 lattice could be an effective strategy to enhance the electrochemical performance of the material. (C) 2020 Elsevier Ltd. All rights reserved.